Direct current electric motors are commonly used to drive a fan or blower in a vehicle ventilating system. Such motors have a rotating shaft which extends through a motor housing having one end carrying a first bearing or bushing supporting one portion of the shaft and an opposed end carrying an end plate. A second bearing or bushing is typically press fit in the end plate and engages an opposed end portion of the rotating shaft.
As shown in FIG. 1, a prior art electric blower motor for a vehicle ventilating system has a fixed part formed of a generally cylindrical housing or metal body shell having a base wall at one end with an enlarged boss which receives the first bearing or bushing. An end plate is fixedly joined to the other end of the housing. Permanent magnets are mounted on the inner surface of the body shell and surround the shaft. Brushes are mounted in an electrically insulating brush holder or card which is disposed adjacent to the end plate. The brushes make contact with a rotating part or armature of the motor which is mounted on the drive shaft.
The second bearing or bushing is mounted in the end plate by means of a bushing retainer plate and a separate clip which holds the retainer plate in a fixed position within the end plate. An oil throw washer and two separate wear washers are mounted within the housing body between the armature and the second bushing. The oil throw washer is shaped to re-circulate lubricant which has been expelled from the lubricant-impregnated second bushing back toward the second bushing.
In addition to the construction described above and shown in FIG. 1, electric blower motors have also been constructed in which the second bearing is fixedly mounted by means of a press fit into the end cap thereby eliminating the bushing retainer and the separate retainer clip.
However, the number of separate parts typically employed in such blower motors, including the separate end plate, second bearing or bushing, bushing retainer clip, the oil throw washer, and the two separate wear washers can create a manufacturing tolerance dimensional buildup which could result in looseness between the individual parts of the motor. This looseness and/or misalignment can cause objectionable vibration and noise which are readily apparent to the vehicle occupant.
Thus, it would be desirable to provide an electric blower motor in which the individual motor brushes, the rear bearing/bushing, and the motor armature are more accurately aligned to minimize vibration and noise. It would also be desirable to provide an electric blower motor wherein any vibration and noise of the rear bearing/bushing and the motor brushes are isolated from the remainder of the motor components. It would also be desirable to provide an electric blower motor in which the end cap and the brush card are integrated into a one-piece assembly to minimize dimensional tolerance buildup and component misalignment.
The present invention is a brush card bushing holder for use in an electric motor used in vehicle ventilation systems which minimizes motor component misalignment and dimensional tolerance buildup for more accurate component alignment and less objectionable vibrations and noise.
In one aspect, the present invention is a vehicle blower motor which includes a housing having first and second ends. A first bushing is mounted in the first end of the housing. A rotatable shaft extends through the first end of the housing toward the second end of the housing and forms part of an armature.
A plurality of brushes are engagable with a commutator carried on the shaft. A one-piece, unitary brush card bushing holder is mounted in the second end of the housing and carries the plurality of the brushes. A second bushing is mounted in the brush card bushing holder and disposed in engagement with the shaft. A portion of the brush card bushing holder acts as an end plate covering the second end of the housing.
Preferably, a plurality of resilient grommets are mounted on the brush card bushing holder and are engagable with the housing when the brush card bushing holder is mounted on the housing to vibrationally isolate the holder and, more particularly, the rear bushing from the housing.
In another aspect, mounting means are carried in the brush card bushing holder for securely receiving and mounting the second bushing in the holder.
The brush card bushing holder of the present invention provides numerous advantages when used in a vehicle blower motor. The holder retains the rear bushing and the plurality of brushes in a one-piece body. This enables the bushing to be aligned with the brushes for tighter tolerance control. In addition, the holder also assists in aligning the armature with the rear bushing and the brushes for tighter tolerance control. This tighter tolerance control eliminates multi-part dimensional build up which could cause misalignment, wear, or movement of the individual components resulting in objectionable noise and vibration.
The present holder is also mounted in the motor housing in a manner to vibrationally isolate the rear bushing and the brushes from the rest of the motor to avoid the transmission of noise and vibrations from the rotating portions of the motor to the housing. The holder better aligns the brushes during the assembly process by using the rear bushing to locate the motor shaft before the brushes are released from a retracted position against the biasing force of the brush springs.
The holder also cooperates with an oil slinger or thrower between the commutator and rear or second bushing by creating a pocket which acts as a recirculating oil path. Any oil or lubricant excreted from the rear bushing is returned by the oil slinger through the pocket and back to the outer surface of the bushing where it is reabsorbed. This prevents the oil from leaking to other electrically conductive portions of the motor, interfering with efficient motor operation or causing objectionable noise.